17.1 build 21 no more waveform

hello, I have the latest build of DV17 installed. The previous build was fine but I have a bug with the latest one there. When I'm in "Color" all scopes (parade, vectorscope...) display but not the waveform.
Any idea?
Thank you very much.

[Peter Chamberlain]

Like a GPU limitation. Please detail your system and GPU driver

Thank you very much for your answer.
Here they are :

iMac (Retina 5K, 27-inch, 2017)
BIG SUR 11.2.2 (20D80)
3,8 GHz Intel Core i5 4 cores
40 Gb 2400 MHz DDR4
Radeon Pro 580 8 Gb
HD 500Gb 2000Gb/s

Rushes on a samsung 1Tb T5
Either 4k 24 or 120, H265 or H264 it no longer displays.
And like I said in my previous message, waveforms were displayed and worked flawlessly in the previous build.
Thank you for your help.

Here's something to check if you haven't already.

Here's something to check if you haven't already.

Thank you so much for your answer.
Both the waveform and the graticule are ok BUT i've noticed that down on the same window I have a "reset" button. I clicked on it and it's OK know. don't know why.
Anyway it's solved but I don't know why with the latest build I had to do this.
> Problem solved.